The present invention relates to cellular radio communications and finds particularly advantageous application to third generation, wideband code division multiple access (WCDMA) cellular radio communications systems.
In cellular radio communication, admission and congestion control for each cell are used to maintain acceptable quality of service for existing mobile user connections in those cells. Admitting too many new connections may result in increased interference between the mobile user connections degrading the quality of service. In such a situation, congestion control mechanisms in the radio access network may discontinue service or reduce the quality of service of some connections. The goal therefore is to admit a new mobile user connection only if there are available resources sufficient to satisfy its service requirements.
One admission control strategy is to set a limit on the number of mobile user connections and to admit a new user only if the total number of users is below that limit, sometimes referred to as “hard capacity.” An alternative is to base admission control on measurements or estimates relating to the actual load of the system, sometimes referred to as “soft capacity.” Soft capacity procedures maybe based on interference measurements. In the uplink direction from mobile to base station, the interference includes both background noise as well as total received power from the transmitting mobiles. The more mobile users transmitting, the more interference, and the higher the uplink load is in that base station's cell.
Interference at the base station is caused both by transmitting mobiles located in that base station cell as well as transmitting mobiles located in other cells, particularly nearby cells. Thus, admission control would be more accurate if it could be based on both intra-cell uplink interference and inter-cell uplink interference. A difficulty here is that neither the intra-cell uplink interference nor the inter-cell uplink interference can be directly measured with reasonable complexity and sufficient accuracy.
Path gain measurements made (directly or indirectly by the mobiles can be used to estimate intra-cell uplink interference and inter-cell uplink interference. Mobile's are normally ordered by the network to often send some type of measurement report to the radio network that includes path gain values (or values from which path gain can be calculated) relating to pilot signals received from nearby base stations. From these path gain measurements, the interference level in a cell can be estimated that takes into account intra-cell uplink interference and inter-cell uplink interference.
An obstacle to using mobile user measurement reports relates to the practice of mobiles only sending such reports to their respective “serving” radio network controller (SRNC). The serving RNC is the RNC that establishes the mobile user connection. In other words, the mobile radio is in a cell controlled by that RNC when the connection is initiated and established. If the mobile user moves to another cell “X” controlled by another RNC, referred to as a drift RNC (DRNC), the mobile's measurement report is nevertheless still directed to the SRNC.
Because the drift RNC lacks the benefit of the information contained in this drifting mobile's measurement report, it cannot formulate a comprehensive determination of the intra-cell and inter-cell uplink interference caused by the uplink transmissions of such drifting mobiles. Without the measurement reports, the drift RNC does not know what impact mobile transmissions from drifting mobiles will have on the uplink load in cell X. A similar problem exists for a mobile that may not have drifted to another RNC's cell, but is still close enough to generate measurement reports relating to one of the other RNC's cells, e.g., cell “Y.” Those measurement reports are sent to the serving RNC but not to the other (cell Y's) RNC. The other RNC therefore does not know what impact that mobile's uplink transmission has on cell Y's total uplink interference load.
One way to solve this problem is for all RNCs to receive all mobile measurement reports. But this would create an enormous and largely unnecessary signaling load. A more efficient approach is for the serving RNC to signal the load contribution of all mobiles for which it is the serving RNC to all cells controlled by another RNC that are affected by the uplink transmissions of those mobiles. This allows the other RNC to determine the contribution of those mobiles to the total uplink interference in its cells. The other RNC can then perform admission or congestion control in one or more of its affected cells using the determined uplink load contribution information.
The serving RNC may receive measurement reports from one or more of the mobile radios periodically, upon the occurrence of an event, or in response to a request from the serving RNC. The measurement reports may include path gain information. The path gain information may be path gain values or values from which path gain values may be determined. Other uplink load measurement parameters may be employed in the uplink load estimation, e.g., mobile UE activity level, target signal quality such as target carrier-to-interference ratio, etc.